With higher demand for organic products, methods for increasing the production of crops without the use of chemical fertilizers, pesticides and herbicides has been of particular interest and importance. Biopesticides used for agricultural purposes have been developed and continue to be developed to control pests and weeds, as well as act as fertilizers, thus increasing plant growth and crop yields without the need for chemicals that can damage the environment and cause safety and/or health concerns. These biological control agents are typically in the form of natural microbes, fungi, or other organisms, and in particular, fungi mycelium. These biological agents have a toxic effect on harmful insects and/or weeds, but do not negatively affect the growing crops, and/or may act beneficially as fertilizers that actually promote the growth of plants with which they are used.
The particular biological control agents used as pesticides act as parasitic microbes that attack the insects or undesirable plant matter causing them to die. By spreading these microbes or biological agents in the soil and fields, these materials can naturally destroy the damaging insects and/or weeds, as well as act as fertilizing agents to facilitate crop growth. Research and development is still underway in determining and isolating effective microbes and biological agents out of the many thousands that exist for use as such pesticides. Therefore their use is only expected to increase over time.
Of those parasitic microbes and organisms that are discovered and isolated for use as biopesticides, they must be produced in large quantities so that they can be used commercially for agricultural purposes. Once such system that is used by large industries involves produces the organisms in bulk. This involves the use of a large vessel containing a substrate. The substrate is a nutrient food source that a microbe, fungi, or particular organism prefers and when introduced into this substrate will tend to grow particularly rapidly on such substrate. In order to be used for cultivation the substrate must be sterilized to eliminate the growth of other undesirable microbes. To do this, the vessel with the substrate is typically heated to ≥121° C. for a certain length of time. This is typically accomplished with the use of live steam. The amount of time for sterilization depends on the amount of substrate being sterilized. After sterilization, the vessel and substrate are cooled. The pure, isolated microbe or biological agent, such as fungi mycelium, which may be previously grown in petri dishes or test tubes are then added to the substrate within the vessel. The vessel then slowly rotates and mixes the materials until they are homogenously mixed together.
Once the materials are mixed, the mixture is introduced into bags in suitable amounts and allowed to incubate at a desired temperature and humidity to promote growth of the particular microbes or other organisms. Incubation is typically complete when the substrate is completely consumed. Incubation is ended by drying the bag contents, which typically occurs under vacuum. After drying, the resulting dried microbial material is crushed and reduced in size to desired particles sizes.
While the large bulk processing systems are useful in producing large quantities of microbial materials useful as biopesticides, they have shortcomings. Such bulk systems are expensive and difficult to use, making them practical only for large producers. Furthermore, the bulk vessel is susceptible to contamination. If even one contamination spore enters the bulk vessel after sterilization, such as during introduction of the desired microbe that is being cultivated, the whole batch may be rendered unusable.
A more affordable method that can be used by smaller producers does not make use of a bulk vessel. Instead smaller plastic bags filled with substrate are used that can withstand the temperatures of sterilization (i.e., ≥121° C.) for a sufficient amount of time to sterilize the substrate. The bags may have a small filter to allow steam used for sterilization to escape during the sterilization procedure so that the bag does not explode or burst as it is heated. If no filter is used, the bag may be positioned upright with one end of the bag being open but with the opening restricted with either a foam or cotton wool material to allow the escape of steam.
Once the sterilized substrate is cooled, pure microbes or organisms to be cultivated are introduced into the bag. If a filtered bag is used, the open end is sealed, such as by welding. The bag and its contents are then agitated to mix the materials and the bag is placed on a shelf for incubation.
After incubation, the bag is cut open and the contents are poured into a second drying bag. Drying typically occurs with dry heating under a vacuum within a vacuum chamber for increased efficiency. Drying in bags is more suitable than in industrial drying, which involves higher temperatures, which can kill off the microbes that have been cultivated. The drying bag must be constructed to allow water vapor to readily escape while retaining the bag contents within the bag. Thus, the drying bag must have a large area of filter material to allow the water vapor to escape efficiently and quickly. The requirement of needing a second drying bag, however, adds additional costs and labor, as the ripe microbes from the incubation bag must be transferred to the drying bag to facilitate drying.
To overcome the shortcomings of the above-described methods, improvements are needed.